Peptide microarrays are a valuable antibody screening tool. A peptide microarray is able to distinguish antibodies specific to closely related peptides and proteins. For example, somatic mutations produce mutant proteins (neoantigens) which can be recognized by an antibody. A peptide microarray can distinguish an antibody against a neoantigen from an autoantibody specific for a wild-type protein. The latter can potentially be a marker for autoimmune disease.
Autoimmune diseases are characterized by immune responses of an organism against its own cells and tissues. Autoimmune diseases include celiac disease, type I diabetes, systemic lupus erythematosus (SLE), Addison's disease, rheumatoid arthritis, and several others. Autoantibodies—antibodies against a body's own antigens—are the cause of many autoimmune symptoms as well as a diagnostic marker for these conditions. Sensitive detection of autoantibodies is essential for correct and timely diagnosis and symptom management of autoimmune diseases.
Neoantigens are new proteins and peptides resulting from somatic mutations in the genome. Neoantigens are often generated in tumors, including malignant tumors in the course of malignant transformation and tumor progression. These new antigens are a dominant target for tumor-infiltrating lymphocytes (TILs). Identifying these antigens and antibodies specific to them holds potential for personalized cancer immunotherapy. Therapeutic vaccination with neoantigens has been shown to produce anti-tumor immune response (Senci, M., et al., 2006. Unique tumor antigens: evidence for immune control of genome integrity and immunogenic targets for T-cell mediated patient-specific immuno-therapy. Clin. Cancer Res. 12:5023).
One way of identifying neoantigens is whole-genome exome sequencing to reveal mutated coding sequences. Computational analysis is then used to determine which of the mutated peptides will be good antigens, i.e., are likely to fit into the cleft of the patient-specific HLA Class I molecule (Hacohen, N., et al., 2013. Getting personal with neoantigen-based therapeutic cancer vaccine Cancer Immunology Research 1:11). One study was able to validate that neoantigens are immunogenic by exposing CD8+ T-cells from the patient to antigen-presenting cells (APC) pulsed with a mixture of in vitro synthesized neo-antigen peptides and then testing for T-cell activation (Rajasagi M., et aL, 2014. Systematic identification of personal tumor-specific neoantigens in chronic lymphocytic leukemia, Blood 124:453). In this emerging field of cancer therapy, there is a need to quickly and reliably identify which tumor-specific peptides are immunogenic and have therapeutic potential.
Screening serum antibodies using peptide microarrays provides valuable diagnostic information about the subject. More generally, a peptide microarray can characterize antibodies in a polyclonal serum or one or more isolated antibodies with respect to their antigens. There is a need for a reliable system of interrogating antibody specificity by presenting multiple variations of the same peptide sequence.